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ANSWERS: OCR Physics B(Advancing Physics) G491~ 20th May 2014~ AS Physics Watch

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    (Original post by Mutleybm1996)
    Are you folks still at school? Could you ask your teachers if we need to know how to apply image processing techniques such as smoothing,edge detection and noise removal using the formulae in the book? I emailed my teacher but she's not in school until after the exam apparently and i can't find it in the specification(which we all know is rubbish)
    I came across a question where we needed to know the effects that they had on an image, but the only ones where we need to apply them are usually really simple.
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    (Original post by H0PEL3SS)
    I came across a question where we needed to know the effects that they had on an image, but the only ones where we need to apply them are usually really simple.
    So we have to remember them and be able to apply them?
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    (Original post by Mutleybm1996)
    So we have to remember them and be able to apply them?
    Pretty much. We need to know what they are and how they work. Applying them is rarely needed.
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    (Original post by H0PEL3SS)
    Pretty much. We need to know what they are and how they work. Applying them is rarely needed.
    I love how your username very accurately describes how I feel about this Physics exam
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    (Original post by Knowing)
    I love how your username very accurately describes how I feel about this Physics exam
    :laugh: I don't feel as badly as I did a month ago, though.
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    (Original post by Mutleybm1996)
    Are you folks still at school? Could you ask your teachers if we need to know how to apply image processing techniques such as smoothing,edge detection and noise removal using the formulae in the book? I emailed my teacher but she's not in school until after the exam apparently and i can't find it in the specification(which we all know is rubbish)
    Yep, still at school. My next physics lesson is on Thursday though so I won't know until then. The specification does say that: "Candidates are not expected to carry out numerical manipulations in the examination; an understanding of the nature of the processes will be sufficient".

    In past papers, I've only seen instances where the give two images and ask you to compare between them and the June 2013 paper had very simple calculations. Still, I will double check on Thursday with my teacher
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    I reckon I have all the theory down, but i consistently get low 50's in past papers. The mark scheme seems to want extremely specific answers to questions. The lack of support from revision aids e.g. a good textbook doesn't help either. Pretty worried about this exam tbh
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    (Original post by shloke123)
    I reckon I have all the theory down, but i consistently get low 50's in past papers. The mark scheme seems to want extremely specific answers to questions. The lack of support from revision aids e.g. a good textbook doesn't help either. Pretty worried about this exam tbh
    The textbook is awful. I haven't opened it once.
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    Hey, has anyone been able to find the June 2013 paper online anywhere?
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    (Original post by Ed4)
    Hey, has anyone been able to find the June 2013 paper online anywhere?
    I've attached the paper and mark scheme.
    Attached Images
  1. File Type: pdf pia m 2013.pdf (541.8 KB, 182 views)
  2. File Type: pdf G491_MS_June13.pdf (225.9 KB, 764 views)
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    (Original post by ZahraP)
    I've attached the paper and mark scheme.
    That's awesome, Thanks very much!
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    Hey guys, does anyone know how much we need to know about Bandwidth for this exam (as the frequency of a signal) - there's nothing on my revision guide? Thanks
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    (Original post by Jamie001)
    Hey guys, does anyone know how much we need to know about Bandwidth for this exam (as the frequency of a signal) - there's nothing on my revision guide? Thanks
    we pretty much need to know that it's just the range of values within a signal.
    "Bandwidth is the frequency of a signal. Although original signals have varying frequencies, when these are transmitted, for example, as FM radio waves, they are modulated so that they only use frequencies within a certain range. FM radio modulates the frequency of a wave, so it needs some variation in the frequencies to allow for transmission of multiple frequencies. Since bandwidth is a frequency, it is the number of bits per. second. The bandwidth required to transmit a signal accurately can be calculated by using 1 as the number of bits, giving the formula:

    where B is bandwidth (in Hz), and t is the time taken to transmit 1 bit of data (in s).
    The bandwidth of a signal regulates the bit rate of the signal, as, with a higher frequency, more information can be transmitted. This give us the formula (similar to the formula for lossless digital sampling):
    b = 2B
    where b is the bit rate (in bits per. second), and B is the bandwidth (in Hz)."

    http://en.wikibooks.org/wiki/A-level...ics)/Bandwidth
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    If anyone has any questions as they are going through exam paper or the course in general, please ask
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    (Original post by Kuna9613)
    we pretty much need to know that it's just the range of values within a signal.
    "Bandwidth is the frequency of a signal. Although original signals have varying frequencies, when these are transmitted, for example, as FM radio waves, they are modulated so that they only use frequencies within a certain range. FM radio modulates the frequency of a wave, so it needs some variation in the frequencies to allow for transmission of multiple frequencies. Since bandwidth is a frequency, it is the number of bits per. second. The bandwidth required to transmit a signal accurately can be calculated by using 1 as the number of bits, giving the formula:

    where B is bandwidth (in Hz), and t is the time taken to transmit 1 bit of data (in s).
    The bandwidth of a signal regulates the bit rate of the signal, as, with a higher frequency, more information can be transmitted. This give us the formula (similar to the formula for lossless digital sampling):
    b = 2B
    where b is the bit rate (in bits per. second), and B is the bandwidth (in Hz)."

    http://en.wikibooks.org/wiki/A-level...ics)/Bandwidth
    Great thanks Have you seen June 2013 Q9(b)(iii)? must the bandwidth be significantly lower than the carrier frequency?
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    Well it is high enough to cope because the frequency is much greater than the bit rate.

    The bandwidth needs to be around the same value as the bit rate, so therefore the bandwidth is significantly lower than the carrier frequency as you said. Tbh i'm a bit stuck in that one too, as i'm not sure how to do a calculation for it :/
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    I don't understand how we are meant to know whether the bandwidth of signal is large enough to transmit a certain number of bits. I was doing a paper and it said 'Why is data compression needed to be able to transmit a hour worth of HD Tv signal in the 10MHz bandwidth'. I had all the information for the amount of bits for 1 hours of HD TV but i don't know how large a bandwidth is needed to submit that. Oh and also, when the number of sampling levels is restricted by the ratio of total V to noise V, is number of bits supposed to be rounded up or down after you do log2(Vnoise/Vtotal). Thanks
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    (Original post by shloke123)
    I don't understand how we are meant to know whether the bandwidth of signal is large enough to transmit a certain number of bits. I was doing a paper and it said 'Why is data compression needed to be able to transmit a hour worth of HD Tv signal in the 10MHz bandwidth'. I had all the information for the amount of bits for 1 hours of HD TV but i don't know how large a bandwidth is needed to submit that. Oh and also, when the number of sampling levels is restricted by the ratio of total V to noise V, is number of bits supposed to be rounded up or down after you do log2(Vnoise/Vtotal). Thanks
    Round upwards even if it's 7.45... Just round up to 8 as it's the MINIMUM amount of bits and log(Vt/Vn) gives you the exact number of bits.

    As for bandwidth it needs to be >> the maximum frequency(assume that 1 bit is carried on one wave and the Hz is the number of waves per second)


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    As we're the first year to not have January exams (ie: I would have taken G491 if we had January exams), will the grade boundaries change to reflect the extra 5 months of preparation?

    I'm hoping an A is ~45.
 
 
 
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